The present invention relates to arthroplastic reconstruction of the human joints and more particularly to implant resection arthroplasty of the wrist joint.
Surgical treatments of arthritis and similar conditions of the wrist joint have included intercarpal fusion, wrist fusion, local resection, proximal row carpectomy, bone grafting, radial styloidectomy, radial shortening or ulnar lengthening and soft tissue interposition arthroplasty. Fusion procedures affect stability, power and mobility of the wrist. Local resection procedures, which involve removal of bone, are complicated by migration of adjacent carpal bones into the space left by the resection which results in unwanted instability.
Various forms of flexible implants formed from silicone rubber have been developed to replace the lunate bone of the carpal row. Such implants are designed to act as articulating spacers capable of maintaining the relationship of adjacent carpal bones after excision of the lunate while preserving mobility of the wrist. An example of one such prior lunate implant is found in U.S. Pat. No. 4,164,793, entitled LUNATE AND IMPLANT and issued on Aug. 21, 1979 to the present inventor. The implant disclosed therein includes a one piece body of resilient material defining a planar triquetrum face. The face has a generally U-shape in plan and includes a stabilizing stem extending outwardly from and perpendicular thereto. The implant body, in addition, defines a scaphoid face, a cupped, concave, smooth distal surface, a proximal surface, a dorsal surface and a palmar surface. The stem extending from the triquetrum face is adapted to be inserted into an opening formed in the triquetrum bone. The stem helps in stabilizing the bone and retaining it in the correct position.
In certain situations, it has been determined that a semi-rigid or a rigid, metal implant is advisable. With a rigid material, a stabilizing stem cannot be inserted into an adjacent bone. The rigid stem could cut or damage adjacent bone structures. In certain situations, the stabilizing stem of the flexible implants has caused some erosion. It would be advantageous to avoid having to enter adjacent bone structures. Heretofore, proper stabilization of the implant has not always been readily achievable.